properties of crystals

Ionic:

• Properties:

  • High melting and boiling points

  • Hard and brittle (breaks easily when pressure is applied)

  • Conducts electricity only in molten state or when dissolved in water (due to free-moving ions)

  • Soluble in water

  • Forms crystal lattice structures

  • High lattice energy due to strong electrostatic forces between ions

Covalent:

Properties:

• Low melting and boiling points

• Soft or liquid (depending on molecular size)

• Does not conduct electricity (no free-moving ions or electrons)

• Solubility varies (polar covalent compounds are soluble in water, non-polar covalent compounds are not)

• Low lattice energy compared to ionic compounds

• Electrons are shared between atoms, resulting in distinct molecular shapes (polar or non-polar)

Polar Covalent:

• Properties:

  • Moderate melting and boiling points

  • Soft to moderate hardness

  • Does not conduct electricity in solid form

  • Soluble in polar solvents (e.g., water)

  • Unequal sharing of electrons, causing partial positive and negative charges on the atoms

  • Intermediate electronegativity difference (usually between 0.5 and 1.7)

Non-Polar Covalent:

• Properties:

  • Low melting and boiling points

  • Soft

  • Does not conduct electricity (no free ions or electrons)

  • Insoluble in water (soluble in non-polar solvents)

  • Equal sharing of electrons between atoms

  • Electronegativity difference is less than 0.5

Metallic:

Properties:

• High melting and boiling points

• Good conductors of electricity (due to free-moving "sea of electrons")

• Malleable and ductile (can be shaped into wires and sheets)

• Lustrous (shiny) appearance

• Moderate to high hardness

• Electrons are delocalized, forming a "sea" of electrons around metal ions that allows conductivity and malleability

Covalent Network (Giant Covalent Structures):

Properties:

• Very high melting and boiling points

• Very hard

• Do not conduct electricity (unless they are graphite or graphene)

• Insoluble in most solvents

• Atoms are covalently bonded in a continuous network (e.g., diamond, quartz)

• Strong bonds extend throughout the structure

Solid Molecular:

• Properties:

  • Low melting and boiling points (generally lower than ionic or covalent network solids)

  • Soft (easily deformed)

  • Non-conductive (no free ions or electrons)

  • Soluble in non-polar solvents, but insoluble in polar solvents (depends on polarity of the molecules)

  • Held together by weak intermolecular forces, such as London dispersion forces, dipole-dipole forces, or hydrogen bonding (depending on the substance)

  • Distinct molecules: The solid consists of molecules held together by intermolecular forces, rather than a network of atoms or ions.

Properties:

• Low melting and boiling points (generally lower than ionic or covalent network solids)

• Soft (easily deformed)

• Non-conductive (no free ions or electrons)

• Soluble in non-polar solvents, but insoluble in polar solvents (depends on polarity of the molecules)

• Held together by weak intermolecular forces, such as London dispersion forces, dipole-dipole forces, or hydrogen bonding (depending on the substance)

• Distinct molecules: The solid consists of molecules held together by intermolecular forces, rather than a network of atoms or ions.